1. Field of the Invention
The present invention relates to a waterproof recording material and its manufacturing method and, more particularly, relates to a waterproof recording material, which can be manufactured cheaply and easily, having imparted thereto various surface properties such as irregularities, wettability, printability, writability and coating property and visual effects such as stereo patterns or perspective patterns provided by combination of stepwise control of luster and tone.
Waterproof materials of the present invention are particularly suited as security recording materials enabling one to distinguish false from true valuable securities or the like or ensuring against illegal use or use for evil purposes such as altering or falsifying.
2. Description of the Prior Art
As waterproof recording materials, synthetic papers have hitherto been used but so far those used are, for instance, (1) a PET film with its surface roughened by sandblasting, (2) a synthetic resin film with its surface coated with some inorganic chemical, (3) a mixture of a polypropylene resin and an inorganic chemical filmed and drawn or orientated, (4) a paper with a thin synthetic resin layer formed thereon and sandblasted and (5) a paper extrusion-laminated with a polypropylene resin by the use of a matte roll. Of these, however, synthetic paper (1) has drawbacks of the resin used being expensive and the manufacturing process comprising many steps, the latter being the case also with synthetic papers (2), (3) and (4), and their manufacturing costs are inevitably expensive. Synthetic paper (5) is easy to manufacture, indeed, but it cannot well meet the requirements for a recording paper and is poor in workability due to its tendency to be easily charged electrostatically.
Meanwhile, as a method of imparting visual effect background patterns to a synthetic paper using some synthetic resin film, embossing has been used widely. A common method of embossing, however, consists in preheating a sheetlike material, imparting irregular patterns to its surface by the use of an embossing roll with given patterns engraved therein and winding after cooling. This process for manufacturing the waterproof recording material having ground patterns comprise two steps, this making the manufacturing process complicated and the productivity low.
Nowadays, various gift cards such as gift certificates, beer cards and white shirt cards, capital or fund securities (investment securities) such as stock securities, debentures and government bonds, monetary certificates such as bills and checks, goods certificates such as cargo exchanges and warehouse bonds, various admission tickets, and cards such as ID cards and prepaid cards are used widely and in large quantities and they are no longer dispensable in our daily life.
Of these, the gift certificates, cards and the like allow users to obtain goods or service without carrying cash, and allow member stores to save effort and expense for sales promotion and bill collecting. Also card issuing firms can have commissions and banks can anticipate increase of deposits as well as loans and omission of credit survey, thus the system being profitable for all those concerned. Since such system can work, needless to say, on the premise of social credit, however, illegal use of false or altered cards and the like is truly fatal and crimes involving illegal use of such cards have come to be a graver social problem in proportion to the spread of the system. In the case of the aforementioned capital securities or monetary certificates, in particular, the amounts of money are quite large and the influence that the illegal use or abuse of such certificates and the like has on the society is quite grave. For prevention of such illegal use, there is a method of using the so-called watermark, but this method cannot be easily used since it requires a highly advanced technique and, further, there are legal limitations set therefor. As safeguard against illegal use of cards and the like, the insurance system is widely used but this is an ex post facto conduct having nothing to do with prevention of crimes such as illegal use or abuse of cards and the like.